Page 162 - RoadCem Manual - PCT BV

stabilized soils contain minimum amount of clay and organic materials. Slurry only treatment is best suitable for sandy soils stabilized with RoadCem and Cement.
5.9.7 Other Surfacing Options
Other bituminous surfacing options such as Otta Seal and Asphalt Concrete (AC) can also be used, Table 5.9 gives general guidelines for required inputs to achieve good results.
Table 5.9 All types of sprayed surfacing, such as surface dressings, Otta seals and sand seals
Required input for achievement of a good results (Low Moderate High)
Surface dressing
Otta seal
Sand seal
Slurry
AC 4)
Skills
Moderate
Moderate
Low
Moderate 3)
Un-suitable
Equipment, Spreading
Moderate
Moderate
Low
Low
Un-suitable
Equipment, Bitumen Applications 1)
Moderate
Moderate
Low
Low
Un-suitable
Materials quality
High
Moderate
Low 2)
Moderate/High
Un-suitable
1) A bitumen distributor is required for most sprayed seals. Hand sprayers are an alternative, especially when using emulsions, but spray rates need to be controlled. Mixing slurry in concrete mixers is preferred, even when laying by hand. Selfpropelled slurry machines increase efficiency but a much higher cost.
2) Coarse sand, sometimes available by screening, can increasae the material quality to “moderate” where sand seals are used alone as permanent seals. Where sand seals are used as cover seals, the material quality requirements can be reduced to “low”.
3) The selection and handling of bitumen emulsions, including proportioning and adjustment of consistency, increases the need for handling skills. Training is usually required.
4) Although included for comparison with other seal types, surfacing with AC is usually confined to areas with wet climates and/or steep terrain.
These type of sprayed surfaces all follow a similar construction procedure:
• Priming of the base (may sometimes be omitted).
• Base repair (chip and spray by hand using emulsion) to even out the occasional rut caused by a stone under the motor grader blade.
• Spraying of bituminous binder.
• Spreading of aggregate. 162